1. Field of the Invention
The present invention relates to a rotor cooling device of a superconducting rotating machine (e.g., power generator or electric motor). More particularly, the present invention relates to a piping configuration of a cooling line through which a cooling fluid passes, in a rotor cooling device of a superconducting rotating machine, based on a forced convection-using fluid circulation method.
2. Description of the Prior Art
A superconducting rotating machine (e.g., power generator or electric motor) is a rotating machine including a rotor with a superconducting wire, instead of with a general copper wire, and thus can be manufactured as a smaller and lighter machine than a conventional rotating machine. On the outer surface of the rotor for the superconducting rotating machine, a bobbin block around which the superconducting wire is to be wound is provided. Since such a superconducting rotating machine requires the use of superconductivity, the rotor has to be cooled to a superconducting temperature.
A rotor cooling method is divided into a natural convection-using method and a forced convection-using method.
The forced convection-using method is divided into a method of circulating a low temperature gas by a blower, and a method of circulating a low temperature cooling fluid by a fluid supply means.
The gas circulating method is not subjected to gravity, but is accompanied with problems, such as a low cooling efficiency, and leakage of high pressure gas. Meanwhile, the liquid circulating method has a high cooling efficiency due to the use of evaporation latent heat by a phase change (from liquid to gas), but may cause non-uniformity in the flow by the fluid's own gravity.
Meanwhile, a cooling method using a fluid (e.g., gas or liquid) forced convection has a structure where a rotor is separated from the fluid supply means side. In the structure, a cooling fluid path at the fluid supply means side is fixed, and a cooling fluid path at the rotor side is rotated at a high speed.
Accordingly, between the cooling fluid path at the high-speed rotating superconducting rotor side, and the cooling fluid path at the fixed fluid supply means side, a special connection, such as an interconnecting dynamic sealing device, is required. However, in such a special connection, significant heat loss is caused, and thereby there is a problem in that an expensive cryogenic refrigerant is required to be occasionally filled. Besides, the reliability may be reduced in long time operation.
Therefore, in the fluid forced convection-based cooling device of a superconducting rotating machine, it is required to improve the cooling fluid path structure of the connection between the cooling fluid path at the fixed fluid supply means side and the cooling fluid path at the rotating rotor side.